The invention relates to an agglomerated stone for using in shaft, corex or blast furnaces, to a method for producing such agglomerated stones as well as to the use of fine and superfine iron ore dust.
In the extraction, dressing, preparation and processing of ore, large quantities of fine and superfine iron ore dust having a particle size of up to 3 mm occur. In order to be also able to use this dust for metal production, it must be converted into a stone format. Usual methods for making stones from fine and superfine ore used in the metallurgical industry are sintering and pelletising.
In order to sinter iron ore dust, a mixture of dampened fine ore as well as coke slack or another carbon carrier and limestone, quicklime, olivine or dolomite aggregates are usually spread onto a circulating grate, the so-called “sintering belt” and fired from above. Carbon contained in this mixture incinerates with the aid of the air drawn by the sintering belt and thus causes agglomeration of the ore particles. On reaching the end of the sintering belt the layer lying on the belt is completely sintered in this way. The solidified iron ore is broken up, sieved in the still glowing state and fed to a cooler, where it is gently cooled so that its hardness is not impaired. The sinter obtained after further sieving the fine components of the cooled sinter mixture, due to high gas permeation and good reducibility, is suitable for direct charging in the blast furnace.
With the known sinter method iron ore dust can usually only be converted economically into a stone format, if its particle size is 2 mm or more. Iron ore dust having substantially smaller particle sizes can be used for metal production by pelletising.